1. Field of the Invention
The present invention relates to a film-forming apparatus for forming a functional deposited film on a substrate. The present invention also relates to a vacuum processing apparatus and a vacuum processing method for vacuum-processing an object. Still more particularly, the present invention relates to a roll-to-roll type continuous film-forming apparatus having a plurality of vacuum chambers communicated with each other, which enables one to continuously form a functional deposited film on an elongated substrate such as a substrate web by continuously transporting the substrate in the longitudinal direction to sequentially pass through said plurality of vacuum chambers while forming a desired functional deposited film in each vacuum chamber. The film-forming apparatus is suitable particularly for continuously forming a semiconductor element such as a photovoltaic element including a solar cell.
2. Related Background Art
For the continuous formation of a functional deposited film on a substrate which is suitable for use in the production of a photovoltaic element including a solar cell, there are a number of proposals in which a plurality of deposition chambers are provided such that they are communicated with each other, and an elongated substrate (a substrate web) is continuously moved to sequentially pass through said plurality of deposition chambers while forming a desired functional deposited film on the substrate by each deposition chamber. For instance, U.S. Pat. No. 4,400,409 (hereinafter referred to document 1) and U.S. Pat. No. 5,510,151 (hereinafter referred to as document 2) disclose a method and an apparatus for continuously forming a photovoltaic element on an elongated substrate, i.e., a substrate web by way of a roll-to-roll film-forming process. Particularly, these documents 1 and 2 describe that using a film-forming apparatus comprising a plurality of vacuum vessels capable of being vacuumed and a plurality of film-forming chambers having a discharge region each provided in one of said plurality of vacuum vessels wherein said plurality of vacuum vessels are communicated with each other, a substrate web having a desired width is transported in the longitudinal direction and along a prescribed pathway for the substrate web to be moved to sequentially pass through the film-forming chambers each provided in the vacuum vessel while forming a desired deposited film on the substrate web by each film-forming chamber, whereby an element having a semiconductor junction can be continuously formed on the substrate web. Specifically, the film-forming apparatus described in documents 1 and 2 is structured such that the vacuum vessels each having the film-forming chamber provided therein can be evacuated to maintain their inside at a reduced pressure and the substrate web can transported while being held so as to serve as an upper wall of each film-forming chamber. In each of the film-forming chambers each provided in one of the vacuum vessels, a raw material gas and an electric power(such as a high frequency power) for exciting or decomposing said raw material gas are introduced therein to form a desired deposited film on the substrate web by way of plasma CVD, sputtering or the like.
Incidentally, in the film-forming apparatus comprising a plurality of vacuum vessels capable of being vacuumed and a plurality of film-forming chambers having a discharge region each provided in one of said plurality of vacuum vessels wherein said plurality of vacuum vessels are communicated with each other, a substrate web having a desired width is transported in the longitudinal direction and along a prescribed pathway for the substrate web to be moved to sequentially pass through the film-forming chambers each provided in the vacuum vessel while forming a desired deposited film on the substrate web by each film-forming chamber, it is known, as disclosed, for instance, in Japanese Unexamined Patent Publication No. 181005/1977, that each film-forming chamber is provided with a slit-like opening at each of its opposite sides through which the substrate web is moved, and an opening-adjusting member having a slit which allows the substrate web to pass through is provided at the slit-like opening for determining the width of the slit-like opening, wherein the slit-like opening provided at one film-forming chamber is communicated with a passage way for the substrate web which is communicated with another slit-like opening provided at the other film-forming chamber which is situated adjacent to said film-forming chamber. The opening-adjusting member also serves to restrict the extent of a region for the substrate web to be exposed to a plasma or the like in the film-forming chamber, namely, the area of a film-forming region in the film-forming chamber in order to control the thickness or property of a film deposited on the substrate web in the film-forming chamber.
The opening-adjusting member further serves to prevent a raw material gas and excited species thereof and a high frequency power for exciting said raw material gas in the film-forming chamber from being leaked outside the film-forming chamber.
In the present invention, attention is focused on the functions of the opening-adjusting member to allow the substrate web to pass therethrough into the film-forming chamber while preventing the raw material gas, the excited species thereof, and the high frequency power in the film-forming chamber from being leaked outside the film-forming chamber.
By the way, the height of the slit of the opening-adjusting member, that is, the clearance of the opening-adjusting member is usually extremely narrowed to an extent of several millimeters. In order to improve the characteristics of an element to be formed on the substrate web, it is necessary to adequately change particularly the inner pressure in each film-forming chamber upon film formation, and in the case where the electric power introduced into a given film-forming chamber is increased, it is necessary to have a due care so that the plasma is confined within the film-forming chamber. In this connection, it is desired that the slit-like opening is made have a cross section which is as smaller as possible and its length in the transportation direction of the substrate web is prolonged.
As the substrate web, it is usually use a substrate web which has a thickness which is sufficiently thin with respect to the width and a sufficiently long length and which has a substantially flat surface at room temperature where no external pressure is applied thereon. In the case where the film-forming chamber is shaped in a rectangular form whose upper side is open while maintaining the substrate web in a plane state by applying a prescribed tensile force thereto in the longitudinal direction, the substrate web is transported such that it serves to establish a upper wall for the film-forming chamber.
Incidentally, the above described film-forming technique have such disadvantages as will be described below.
That is, a prescribed heater is provided in each film-forming chamber in order to heat the substrate web to a desired temperature. Because of this, there is an occasion in that the substrate web heated by the heater is spontaneously deformed in a bow or wave form to have a flexture.
As one of the causes of occurring such flexture for the substrate web, there is known a situation such that in the case where the substrate web which is transported in the longitudinal direction of the film-forming apparatus is heated in the film-forming chamber, the substrate web is sometimes partially thermally expanded in its width direction, and other portion of the substrate web is shrunk by being cooled, where displacement is occurred at the substrate web in a direction perpendicular to the surface of the substrate web, whereby a portion of the substrate web which corresponds the thermally expanded portion in the width direction is relaxed and as a result, the substrate web is deformed as above described. As another cause, there is an occasion in that a stress is occurred between a film deposited on the surface of the substrate web by heating the substrate web and the substrate web itself, whereby the substrate web is deformed as above described.
When the substrate web is deformed as above described and it is contacted with the opening-adjusting member, a cut defect is liable to occur at the substrate web which is transported. Particularly, when the deposited film-bearing face of the substrate web is contacted with the opening-adjusting member, there will be an occasion for the deposited film to be damaged. In the case where a photovoltaic element is prepared using the deposited film having such damage, the photovoltaic element is liable to have a defect such that a short-circuited defect will occur at the damaged portion of the deposited film constituting the photovoltaic element. Separately, when the face with no film of the substrate web is contacted with the opening-adjusting member, there is an occasion in that the substrate web or/and the opening-adjusting member are partially cut to cause a powdery material, which will be a cause of generating dust in the film-forming chamber.
In order to deal with such problems, Japanese Unexamined Patent Publication No. 181005/1997 (hereinafter referred to document 3) discloses a means of forcibly remedying the configuration of the substrate web to a desired curved form, where certain expected effects are obtained. Particularly, document 3 discloses a method in that a substrate web having magnetism is transported while being supported using a magnet roller which is shaped not in a cylindrical form but in a form having a continuously varied diameter, wherein the traverse form of the substrate web is forcibly made into a curved form along the external shape of the magnet roller and the opening of the film-forming chamber is shaped to follow said curved form, whereby the substrate web is prevented from being spontaneously deformed by virtue of heat and a prescribed clearance is established between the substrate web and the opening-adjusting member to prevent the substrate web from being damaged by the opening-adjusting member. The opening-adjusting member in this case is configured such that its face which is opposed to the substrate web is entirely curved.
Even for the technique disclosed in document 3, there are still some subjects which are necessary to be solved. That is, in the case where the extent for the substrate web to be spontaneously deformed or the magnet roller is relatively weak in terms of the magnetic force, there is an occasion in that the substrate web is difficult to be completely remedied into a desired form, where it is difficult to sufficiently prevent occurrence of a flaw at the substrate web. Besides, in the case where especially the inner pressure of the film-forming chamber is changed or the electric power introduced into the film-forming chamber for decomposing the raw material gas therein is increased in order to improve the characteristics of, for instance, a photovoltaic element to be obtained, when the raw material gas or excited species are leaked outside the film-forming chamber or the electromagnetic wave is leaked outside the film-forming chamber, there is an occasion in that a film is deposited on an unnecessary portion of the vacuum vessel which encloses the film-forming chamber or the electric power cannot be introduced into the film-forming chamber as desired.
In order to prevent such leakage, it is necessary to improve the effect of the opening-adjusting member to confine the raw material gas including excited species and the electric power within the film-forming chamber. In order to achieve this purpose, it is desired to adopt measures such that the area of the substantial opening through which the substrate web passes, specifically, the cross section of the opening-adjusting member is diminished as smaller as possible and the length of the opening-adjusting member in the transportation direction of the substrate web is prolonged, whereby the conductance of the position where the opening-adjusting member is provided is diminished and the confining effect of the electromagnetic wave is improved. However, when the height of the slit of the opening-adjusting member is diminished in order to diminish the cross section of the opening-adjusting member, a problem is liable to occur such that the probability for the substrate web to be contacted with the opening-adjusting member is increased even in the case where the magnitude for the substrate web to be deformed is small. And, in the case where the length of the opening-adjusting member in the transportation direction of the substrate web is prolonged, a problem is liable to entail such that even when a slight discrepancy is present at the setting position of the opening-adjusting member or at the passage of the substrate web, there is occurred a portion which makes shorten the distance between the opening-adjusting member and the substrate web such that they come to close each other, where the probability for the substrate web to be contacted with the opening-adjusting member is increased.
Incidentally, in the prior art, in order to solve the problems relating to the contact between the substrate web and the opening-adjusting member, there has been adopted a manner in that the height of the slit, that is, the clearance of the opening-adjusting member is made to be sufficiently large. In this connection, there has been a problem in that the raw material gas in the film-forming chamber is leaked outside the film-forming chamber in the vacuum vessel which encloses the film-forming chamber through the opening-adjusting member and the raw material gas thus leaked is followed by flowing into the adjacent vacuum vessel to contaminate into the film-forming chamber provided therein, where the property of a film deposited on the substrate web is deteriorated. In addition, there has been also a problem in that in order to prevent the excited species or the electromagnetic wave in the film-forming chamber from being leaked outside the film-forming chamber in the vacuum vessel which encloses the film-forming chamber, it is required to diminish the electric power introduced into the film-forming chamber for the decomposition of the raw material gas therein to less than certain upper limit, where the latitude of the electric power introduced is narrowed.
An principal object of the present invention is to solve the foregoing subjects in the prior art and to improve the opening-adjusting member so that an object to be treated is effectively prevented from being contacted with the opening-adjusting member and in addition, processing gas and electromagnetic wave is effectively prevented from being leaked outside the processing chamber.
Another object of the present invention is to provide an improved film-forming apparatus in which a substrate web on which a deposited film is to be formed is effectively prevented from being contacted with the opening-adjusting member upon transporting the substrate web and the effect of the opening-adjusting member to confine raw material gas and electromagnetic wave within the film-forming chamber (the processing chamber) is improved so that the raw material gas and the electromagnetic wave are effectively prevented from being leaked outside the film-forming chamber, and which enables one to continuously form a semiconductor element such as a photovoltaic element including a solar cell having improved characteristics on the substrate web.
A further object of the present invention is to provide a film-forming apparatus which has at least a vacuum vessel whose inside is capable of being vacuumed and a film-forming chamber having a discharge region provided in said vacuum vessel and in which a substrate web is arranged so as to constitute a part of said film-forming chamber, wherein said substrate web is continuously moved to pass through said discharge region of said film-forming chamber to continuously form a deposited film on said substrate web, characterized in that said film-forming chamber is provided with an opening-adjusting member such that said opening-adjusting member constitutes an entrance or/and an exit of said film-forming chamber, and a face of said opening-adjusting member which is opposed to said substrate web has one or more grooves formed substantially in parallel to a direction for said substrate web to be transported.
A further object of the present invention is to provide a vacuum-processing apparatus having a processing chamber whose inside is capable of being vacuumed and in which discharging is capable of being performed, said processing chamber having an opening portion through which an object to be processed being capable of passing between an outside of said processing chamber and said inside of said processing chamber, wherein said opening portion of said processing chamber has an opening-adjusting member for narrowing an opening area of said opening portion, and a face of said opening-adjusting member which is opposed to said object which passes through said opening portion has a recessed portion.
A further object of the present invention is to provide a vacuum-processing method for vacuum-processing an object to be processed in a processing chamber whose inside is capable of being vacuumed and in which discharging is capable of being per formed and which has an opening portion, wherein said method includes a passing step of passing said object between an outside of said processing chamber and an inside of said processing chamber, and in said passing step, said object is passed through an opening-adjusting member whose surface opposed to said object has a recessed portion.